NCERT Solutions for Class 7 Science Chapter 16 Water: A Precious Resource

These NCERT Solutions for Class 7 Science Chapter 16 Water: A Precious Resource Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.

Water: A Precious Resource NCERT Solutions for Class 7 Science Chapter 16

Class 7 Science Chapter 16 Water: A Precious Resource Textbook Exercise Questions and Answers

Question 1.
Mark ‘T’ if the statement is true and ‘F’ if it is false:
a. The freshwater stored in the ground is much more than that present in the rivers and lakes of the world.
b. Water shortage is a problem faced only by people living in rural areas.
c. Water from rivers is the only source for irrigation in the fields.
d. Rain is the ultimate source of water.
Answer:
a. T
b. F
c. F
d. T

Question 2.
Explain how groundwater is recharged?
Answer:
The rainwater and water from other sources, such as rivers and ponds, seeps through the soil and fills the empty spaces and cracks deep below the ground. The process of seeping of water into the ground is called infiltration. The groundwater thus gets recharged by this process.

Question 3.
There are ten tube wells in a lane of fifty houses. What could be the long term impact on the water table?
Answer:
Ten tube-wells in a lane of fifty houses can lead people to mindlessly exploit the groundwater. This can lead to depletion of the water table in the long run.

Question 4.
You have been asked to maintain a garden. How will you minimise the use of water?
Answer:
Drip irrigation can be implemented to reduce the wastage of water. By this process, water is delivered to the base of the plants directly. Pipes should be checked for leaks. Arrangements should be made for collecting rainwater in small pits. This water can be used later for various purposes.

Question 5.
Explain the factors responsible for the depletion of water table.
Answer:
Here are a few factors which are responsible for the depletion of water table:
a. Increased population: As our population increases, correspondingly the demand for water also increases.

b. Increasing industries: The number of industries is on the rise ever since the human population began multiplying exponentially. These industries need water for various processes.

c. Lack of water conservation techniques: Rain is the main source of water for both the surface and the underground water bodies. Upon proper conservation, the ground water can be increased. This has not yet been achieved due to lack of implementation of such water conservative techniques.

d. Agricultural activities: Our country depends vastly on its agricultural roots and the land that is used for the cultivation has increased. Hence, water consumption has also increased. Groundwater is exploited as there is an irregularity in the rainfall. This results in the depletion of groundwater.

Question 6.
Fill in the blanks with the appropriate answers:
a. People obtain groundwater through ……………….. and ………………..
b. Three forms of water are ……………….., ……………….. and ………………..
c. The water bearing layer of the earth is ………………..
d. The process of water seepage into the ground is called ………………..
Answer:
a. wells and tube-wells, b. solid, liquid and gas, c. aquifer, d. infiltration

Question 7.
Which one of the following is not responsible for water shortage?
a. Rapid growth of industries
b. Increasing population
c. Heavy rainfall
d. Mismanagement of water resources
Answer:
c. Heavy rainfall

Question 8.
Choose the correct option. The total water
a. in the lakes and rivers of the world remains constant.
b. under the ground remains constant.
c. in the seas and oceans of the world remains constant.
d. of the world remains constant,
Answer:
d. of the world remains constant.

Question 9.
Make a sketch showing ground-water and water table. Label it.
Answer:

NCERT Extended Learning Activities and Projects

Question 1.
Role play: You are a water detective in your school. You have a team of six members. Survey the campus and make a note of the following.
a. Total number of taps
b. Number of taps leaking
c. Amount of water wasted due to leaking
d. Reasons of leakage
e. Corrective measures taken
Hint:
Do it yourself.

Question 2.
Groundwater pumped out: Try to find out if there are any hand pumps in your neighbourhood. Go to the owner or the users of a few of these and find out the depth at which they struck water. If there are any differences, think of the probable reason. Write a brief report and discuss it in your class. If possible, visit a place where boring is going on to install a hand pump. Watch the process carefully and find out the depth of the water table at that place.
Hint:
There is a difference in depth of water table in difference places. According to the depth of the water table, the pumps are bored to different, depths at different places.

Question 3.
Catching rainwater-Traditional methods: Form groups of 4 to 5 students in the class and prepare a report on the various traditional ways of water harvesting. If possible, use the following web link: www.rainwaterharvesting.org.
Hint:
Do it yourself.

Question 4.
Conservation of water: Carry out a campaign to conserve water at home and in the school. Design posters to remind others of the importance of water resources.
Hint:
Do it yourself.

Question 5.
Create a Logo: Hold a competition to create a logo or a symbol depicting water scarcity.
Hint:
Do it yourself.

Activity 1

Objective: To collect information (articles and pictures) on water shortage from the newspapers and magazines.
Materials Required: Old newspapers and magazines, scrap book.
Procedure:

Collect clipping from newspapers and magazines on the news items, articles, pictures related to water shortage.
Paste them in your scrapbook.

Observation:
Preserve water bodies in the country

Conclusion: The water is very precious for every living being but nowadays there is a shortage of water everywhere around the world.

Forms of Water: in nature, water exists in three forms:

As a solid, it exists as ice-caps at the poles, snow-covered mountains and in glaciers.
As a liquid, it is in the form of water in oceans, lake and rivers, and the underground water.
Its gaseous form is the water vapour in the air around us.

Water Cycle: The water cycle is a natural process that continuously happens on earth. The water cycle maintains the amount of water on the earth. It can be divided into four phases:
i. Evaporation: It is a process when the water from the earth’s surface gets converted into water vapour due to the heat of the sun. The water vapour then goes into the air.
ii. Condensation: The water vapour rises up in the atmosphere and gets accumulated above, condenses and forms water droplets. These droplets collect together and form clouds.
iii. Precipitation: When the volume of droplets increases in the atmosphere, they fall on the earth as rainfall, also called as precipitation. Sometimes it also occurs as snowfall in some areas.

iv. Collection: As the water falls back on the earth, it travels along the surface and gets accumulated at different places like lakes, rivers, seas, oceans and under the ground. That’s how the amount of water is regulated on the earth.

Infiltration: The process of seeping of water into the ground to recharge underground water is known as infiltration.
Aquifer: Sometimes, ground water accumulates between layers of hard rocks. This is known as an aquifer. Water in aquifers can be drawn with tube-wells and hand pumps.
Groundwater: The space between particles of soil and gaps between rocks are filled with groundwater.
Water table: The level below which the ground is saturated with water is called water table. The water table varies from place to place. It may even change at a given place with time.

Depletion of Water Table: As long as the water drawn from the ground is replenished by seepage of rain water, the water table remains unaffected. The problem starts when we take more water from the ground than is replenished by natural means. Then the water table goes down and it is said to have been depleted.

Reasons for the depletion of water table:
The depletion of water table is taking place due to some causes. These causes are:

Increasing population that creates more demand for water.
More wells are dug and water is drawn from them.
Industrial activities are increasing the demand for water. For example, the construction industry uses tube-wells to draw groundwater.
An increase in agricultural activities demands more water. In areas where there are no streams and lakes, groundwater is used for irrigation.

Water Management: It is the continuous matching of water resources with the water requirements of a place. Water management essentially involves activities that identify sources of water, prevent wastage of water, and implement recycling of water. It may also include treatment of water to make it suitable for human consumption. It may include the following exercises:

Prevent wastage of water.
Prevent water leaking from pipes.
Fixing leaking taps.
Prevent water over-flowing from buckets while clothes are being washed alongside.
Using water wisely while brushing the teeth, shaving, bathing, washing and during many other activities,
Practicing rainwater harvesting.

Rainwater Harvesting: Instead of letting rainwater runoff into the sea, it can b>e used to recharge groundwater. This is known as rainwater harvesting. Rainwater harvesting can be used to raise the water table in arid areas. It can also be used to create water storage areas.

Bawris: This is an old method of rainwater storage and recharge. In olden days people built deep step wells into the ground. These deep step wells are called bawris. During rainy season these wells are filled with water. The water is stored in these wells for longer time because they are very deep and the evaporation of water is less. During shortage, people use this water.

Drip irrigation: It can be used by farmers to save water. It is a technique of watering plants by making use of narrow tubing, which delivers water directly at the base of plant.

Effects of Water Scarcity on Plants: Plants need water to absorb nutrients from the soil and make their food. Without water, plants would die and greenery would be lost. This, in turn, would mean the end of all life on the earth. Because without plants, there would have no food, oxygen or rainfall. There would also be many other problems.

Every individual should use water judiciously. Overdrawing of underground water should be avoided and efforts should be made to recharge underground water. To avoid wastage of water in the fields, drip irrigation may be adopted for watering the plants. One should also promote afforestation.

Class 7 Science Chapter 16 Water: A Precious Resource Additional Important Questions and Answers

Very Short Answer Type Questions

Question 1.
Which day is celebrated as the world water day?
Answer:
22 March is celebrated as the world water day.

Question 2.
What is groundwater?
Answer:
The water found below the water table is called groundwater.

Question 3.
What is water table?
Answer:
The upper limit of underground water where all the space between the particles of soil and gaps between rocks are filled with water is called water table.

Question 4.
What are the three forms of water?
Answer:

Solid form: ice, snow
Liquid form: water
Gaseous form: steam or water vapour

Question 5.
Define aquifer.
Answer:
The groundwater stored between the layers of hard rocks below the water table is known as an aquifer.

Question 6.
What is infiltration?
Answer:
The process of seeping of water into the ground is called infiltration.

Question 7.
Why is water cycle important?
Answer:
The water cycle is important because this process provides the earth with the natural, continual water supply that all living things need in order to survive.

Question 8.
What is the source of groundwater?
Answer:
The rainwater and water from other sources, such as rivers and ponds, seeps through the soil and fills the empty spaces and cracks deep below the ground.

Question 9.
What percentage of earth’s surface is covered with water?
Answer:
71%.

Question 10.
Why do certain regions on the earth become desert?
Answer:
Certain regions on the earth become desert because they get very little rain.

Question 11.
Name the available water resource on the earth.
Answer:
Oceans, seas, lakes, rivers, ice, groundwater and moisture in the air.

Question 12.
What is water management?
Answer:
Water management refers to the activities that ensure the continuous matching of water resources with the water requirements of a place.

Question 13.
What do you mean by rainwater harvesting?
Answer:
Instead of letting rain water run-off into the sea, it can be used to recharge groundwater. This is known as rainwater harvesting.

Question 14.
How water in an aquifer can be pumped out?
Answer:
With the help of tube wells or hand pumps.

Question 15.
In which state can the water be found when it circulates through the water cycle?
Answer:
When water circulates through the water cycle it can be found in all the three forms, i.e., solid, liquid and gas (vapour).

Short Answer Type Questions

Question 1.
State various uses of water?
Answer:
Water is used for various activities such as agriculture, industries, cooking, cleaning utensils, bathing, washing clothes and most importantly for drinking.

Question 2.
Why do we need water cycle?
Answer:
The earth is covered by water, however, almost 97% is salt water found in the oceans. We cannot drink salt water or use it for crops because of the salt content. We can remove salt from ocean water but the process is very expensive. Hence, water cycle is required to maintain the flow of fresh usable water on the earth.

Question 3.
What do you mean by drip irrigation?
Answer:
Drip irrigation is a method through which maximum number of plants can be irrigated with minimum use of water. For this, pipelines are laid throughout the rows of plants. Pipes are pierced at strategic points to release water in droplets. This helps in saving the water which is an important but scarce resource.

Question 4.
What is rainwater harvesting?
Answer:
Collecting and conserving the rainwater from the rooftops of the buildings is called rainwater harvesting. In this technique water from the rooftops of the houses, industries, etc., is collected. It is used directly or allowed to seep into the soil instead of allowing it to flow down. It helps in raising the water table.

Question 5.
What are bawris?
Answer:
Bawris was the traditional way of collecting rainwater. Bawris were recharged time to time. With time, they fell into discuss and garbage started piling in these reservoirs. Nowadays, the bawris are being revived.

Question 6.
What will be the consequences if water is not available to the plants?
Answer:
Plants need water to get nutrients from the soil to prepare their food. If water is not available to plants, the green character of the planet shall be lost. This may mean the end of all life, for a world without plants shall mean no food, no oxygen, not enough rain and innumerable other problems.

Question 7.
How increasing industries are responsible for depletion of water table?
Answer:
Water is used by all the industries. Almost everything that we use needs water somewhere in its production process. The number of industries is increasing continuously. Water used by most of the industries is drawn from the ground.

Question 8.
Why is distribution of water uneven in our country?
Answer:
India is a vast country and the rainfall is not the same everywhere. Some regions have excessive rains while some others have very little rainfall. Excessive rains cause floods, whereas the absence of rains results in droughts. Therefore, some regions in our country may have floods while others may suffer from droughts at the same time.

Question 9.
Define water management.
Answer:
Preventing the wastage of precious water is called water management. A couple of techniques can be employed to save precious water.

Construction of Bawris.
Performing rainwater harvesting.
Drip irrigation

Long Answer Type Questions

Question 1.
How is increasing population responsible for depletion of water table?
Answer:
Increasing population creates demand for construction of houses, shops, offices, roads and pavements. This decreases the open areas like parks and playgrounds. This, in turn, decreases the seepage of rainwater into the ground. Moreover, a huge amount of water is required for construction work. Often, groundwater is used for this purpose. So, on one hand we are consuming more groundwater and on the other hand we are allowing lesser water to seep into the ground. This results in the depletion of water table.

Question 2.
What is meant by the water cycle? How water cycles in the nature? Why this cycle is not as straight forward and simple as we discuss in the definition?
Answer:
The whole process in which water evaporates and falls back on the land as rain and later flows back into the sea via rivers is known as the water cycle. It is the circulation of water between the atmosphere and the surface water.

Water evaporates continuously from the surface of seas, rivers, lakes, oceans and vegetation on land into the atmosphere due to the heat of the sun. Water vapours, being lighter, rise upwards and join clouds in the sky. The clouds are carried in the air through long distances. When cooled sufficiently, water vapours condense into water droplets which come down as rain, snow or hail. The rain water finds its way back into the rivers and sea thereby completing the water cycle.

This cycle is not as straight forward and simple as the statement seems to imply. All of the water that falls on the land does not immediately flow back into the sea. Some of it seeps into the soil and becomes part of the underground reservoir of freshwater. Some of this underground water finds its way to the surface through springs. We bring it back to the surface for our use through wells or tube-wells. Water is also used by terrestrial animals and plants for various life-processes.

Question 3.
Discuss some of the steps involved in the conservation of water.
Answer:
The steps involved in the conservation of water are:

Always keep the taps closed while brushing or washing the face to prevent water from flowing away unnecessarily. One should use it only when needed.
Fix any water taps that are leaking, immediately.
Instead of taking a shower, use a bucket to take bath.
Use water left from washing clothes for mopping the floor and washing cars instead of running water.
Water your plants in the morning or evening times so that the water does not immediately get evaporated.
Do not waste food as it takes a lot of water to irrigate the fruits and vegetables.
Do not throw away water unnecessarily. Use water in a judicious manner.

Question 4.
Water is very precious for all living organisms. What will happen in future, if we do not save water now?
Answer:
Water is needed for various life activities. If we continue the misuse and wastage of water and do not conserve it, the life on the earth will get affected. This may lead to consequences such as:

Excessive pumping results in lowering groundwater table.
Groundwater and surface water are connected. When groundwater is over-used, lakes, streams and rivers connected to ground water also get little supply.
Plants need water to prepare their food. If there will be scarcity of water on the earth, the plant will be unable to the prepare their food. This will lead to end of the life because world without plants means no food and no oxygen.

Picture-Based Questions

Question 1.
a. Observe the picture shown below and identify it.

b. Identify all the processes numbered 1-7.
Answer:
a. It shows water cycle.
b.

Source of water
Evaporation
Condensation
Clouds
Transpiration
Infiltration
Rainfall

Question 2.
Observe the given picture and identify it. What is the importance of this process?

Answer:
The given picture shows the drip irrigation. It is an allocation technique used by farmers to water their fields. In this, water is allowed to slowly drip into the plants so that the water directly gets into the roots of the plants. This minimises evaporation, saves water and allows the nutrients to reach the plants easily. Narrow tubes are used to make water reach the roots of the plants in drip irrigation.